A red wagon with a mass of 7\, {\text{kg}}7kg7, start text, k, g, end text is moving with a velocity of 4\,\dfrac{\text{m}}{\text{s}}4 s m 4, start fraction, start text, m, end text, divided by, start text, s, end text, end fraction straight toward a blue wagon at rest. The red wagon’s mass is 777 times the mass of the blue wagon. The final velocity of the red wagon is 3\,\dfrac{\text{m}}{\text{s}}3 s m 3, start fraction, start text, m, end text, divided by, start text, s, end text, end fraction . What is the velocity of the blue wagon immediately after the red wagon collides with it?